Isotherm analyses for single component and multi-component metal sorption onto lignite

The adsorption of the three metal ions, copper, cadmium and zinc in single component and multi-component mixtures in aqueous solutions by lignite is reported. A comparison is made between the single component saturation uptake and the multi-component uptakes. The isotherms indicate a competitive uptake with copper being preferentially absorbed by the lignite in multi-component solutions. The isotherms are plotted to obtain the Langmuir constants, the Freundlich constants and the Redlich–Peterson constants. Lignite is shown to possess an affinity for the metal ions which make its use as an adsorbent a possible alternative to the use of more expensive activated carbons.     

Gas evolution during rapid,low-temperature pyrolysis of a North Dakota lignite

Low-temperature pyrolysis of low-rank coals is proposed as a possible technique for producing high-heating value solids. Results are presented showing gas yields and char compositions from low-temperature pyrolysis of a lignite at very short residence times. Tar evolution is observed even at temperatures less than 570K coinciding with the first release of CO₂, presumably from carboxyl groups.     

Aluminium bromide catalysed transalkylations of a Texas lignite coal

Texas lignite coal was treated at a variety of reaction times and temperatures with water-activated AlBr₃ in the presence of either m-xylene or diphenyl ether. Reactions with m-xylene resulted in increases in coal weights, probably due to incorporation of xylene into the coal structure, whereas reactions with diphenyl ether resulted in weight losses in the treated coal. The solubility in pyridine of the coal recovered from these reactions was increased significantly, reaching a maximum of 50% in one reaction with diphenyl ether. Suggestions are made for processes that may explain both the weight increases and the greater pyridine solubility. Support for the occurrence of transalkylation of alkyl groups from lignite to diphenyl ether was provided by g.c.-m.s. analysis of an ether extract in which diphenyl ether molecules substituted with C₁–C₁₃ alkyl groups could be identified. Also of interest was the observation of the compound phenoxathin among the products of transalkylation.     

Gasification reaction of a lignite char catalysed by Cr,Mn, Fe,Co, Ni,Cu and Zn in dry and wet air

A Spanish lignite was demineralized and pyrolysed in N₂ atmosphere at 1133 K. On the resulting char, metals from Cr to Zn were deposited from nitrates dissolved in ethanol. The behaviour of these supported catalysts in the reaction with dry and wet air was studied by thermogravimetry in the temperature range 733–773 K. To determine the reactivity per unit catalyst surface site, the dispersion of the metals or metal oxides was measured by X-ray diffraction. The dispersion values found were low; the turnover frequencies (TOF) showed that Cu and Cr (probably in the form of Cr₂O₃) are the best catalysts in this reaction when using either dry or wet air. Apparent activation energies were also obtained in the temperature range used; the Arrhenius plot for the copper-char sample shows that in this case the reaction may be diffusion-limited, although there is considerable increase in reactivity close to Tammann's temperature for copper (678 K). Oxygen chemisorption by Cr₂O₃ may justify an oxygen transfer mechanism.     

汽轮机抽汽预干燥褐煤热经济性分析

为实现褐煤提质梯级利用以及褐煤机组大型化,将蒸汽管回转式干燥装置与机组锅炉系统耦合,采用汽轮机低压抽汽作为干燥介质,建立了汽轮机抽汽预干燥褐煤机组经济性分析模型,提出了预干燥所需蒸汽流量与机组经济性评价方法。结果表明,与参考机组相比,采用汽轮机抽汽预干燥工艺将38%水分褐煤分别干燥至27%、20%和14%,采用汽轮机第5级抽汽时机组发电标准煤耗分别增加1.99、3.89和5.05 g/k Wh,采用汽轮机第6级抽汽时机组发电标准煤耗分别增加0.84、2.26和3.31 g/k Wh。汽轮机抽汽预干燥褐煤机组发电标准煤耗普遍增加;褐煤预干燥程度越浅,机组经济性越好;汽轮机抽汽品质越低,机组经济性越好。     

Chemistry of Texas lignite liquefaction in a hydrogen-donor solvent system

To study the nature of chemical cleavage and resultant product transfer from solid lignite phase to liquid phase, autoclave (300 cm³) experiments have been carried out at pressures ranging up to 34 MPa and temperatures of 380–390 °C. The charge to the autoclave was freshly mined wet lignite, tetralin and hydrogen or helium. To obtain an indication of the reaction mechanisms underlying the liquefaction process, liquid and gas samples from the reactor at different time intervals were analysed. The gas samples were analysed by use of a multi-column, multi-valve automated gas Chromatograph, a system specially fabricated for coal-derived gas analysis. The liquid sample was filtered through Millipore filters and separate into three fractions by gel permeation chromatography. Fraction 1 is mostly colloidal carbon and high-molecular-weight species which cannot be separated on a g.c. Fractions 2 and 3 were analysed by gas chromatography — mass spectrometry (g.c.-m.s.). Fraction 2 represents the liquid products released from lignite and fraction 3 is mostly the tetralin and tetralin-derived products. Gel permeation chromatography (g.p.c.) followed by gas chromatography (g.c.) was used to devise a method for monitoring the extent of liquefaction. The production of carbon dioxide is at a maximum before the liquefaction reactions are at a significant rate. The source of carbon dioxide appears to be the carboxylic groups in lignite. The liquefaction reactions consume hydrogen from tetralin which undergoes dehydrogenation to form naphthalene. Once the lignite has undergone depolymerization, the tetralin to naphthalene conversion slows down. The continued heating of lignite conversion products in excess of tetralin does not appear to alter the molecular size distribution of the liquid product. The distillable fraction of lignite-derived liquid is composed of various alkylated phenols and aromatics and alkanes, and they are formed simultaneously.     

褐煤利用技术现状

煤炭是我国最重要的化石能源,其中褐煤资源在我国分布广泛,储量较多。基于我国的能源结构特点和褐煤的煤质特性,论述了褐煤在发展煤制天然气、煤制油、煤热电联产等现代煤化工项目的优势与利用技术,褐煤抽提技术的应用与发展,其中着重介绍了无灰煤技术,其产品具有无灰无水、高发热量等优良性能。还有以褐煤为原料制备新型材料方面的应用,包括褐煤制备吸附剂以及粉煤灰的有效利用,最后提出了我国褐煤现代煤化工以及褐煤高附加值利用应向低能耗、清洁化方向发展。     

Characterization of eluted metal components from coal during pretreatment and solvent extraction

Eluted metals from Enshu (a Chinese) and Stratford (an Australian) coal during pretreatments with methanol/water and dilute acetic acid solutions were characterized and quantitatively analyzed by solid-state ²³Na NMR, cation chromatography, X-ray fluorescence (XRF), and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) measurements. To achieve the requirements of solvent extracted coal (namely Hyper-Coal: HPC) for its direct utilization to gas turbine system, alkali and alkali-earth metals such as Na, K, and Ca should be removed from coals. A quantitative analytical method of alkali metals with ICP-AES in combination with flow injection system is established for the evaluation of remaining alkali metal contents, especially for the quantitative analysis of Na concentration in the original coal and its HPC. Microwave irradiation acidic digestion pretreatment under controlled high pressure and temperature is very essential to the prompt and quantitative analyses of all the metals in coals and their derived HPC. Combination of ICP-AES with XRF and/or cation chromatography is also effective for the respective analyses of the residue and the extract or filtrate. Solid-state ²³Na NMR spectra of the coals before and after solvent soaking pretreatment or acetic acid treatment revealed that ion-exchangeable Na species might be rather selectively eluted by these treatments. It is also suggested that the remaining Na species could not be removed by dilute acetic acid solutions.     

Identification of the combustion behaviour of lignite char between 350 and 900 °C

The combustion behaviour of four different lignite samples pyrolysed at 800 and 1000 °C has been studied. The reaction order and the activation energy of the char combustion reaction can be easily determined from the time to reach 50% conversion. Under 550 °C the reaction order of lignite samples are 0.7 and the activation energies are 27.4–27.9 kcal gmole^?1. Above 550 °C the measurement of the intrinsic reaction rate is limited by the film diffusion resistance. The pyrolysis temperature affects the reactivity significantly. The reactivity of char pyrolysed at 800 °C is 3.5 times that of char pyrolysed at 1000 °C.     

Hydrogenolysis products of pyridine extract of a Japanese lignite

Petroleum ether insoluble fractions of a pyridine extract of a Japanese lignite were pyrolysed with tetralin. The chain length of alkyl groups bonded to aromatic rings and the average chemical structure of aromatic compounds in the lignite were obtained from analyses of hydrogenolysis products. Gas Chromatographic analyses of fractions eluted by cyclohexane showed the presence of C₁₅ to C₃₄ straight-chain alkanes. The chemical structures of the other fractions were analysed quantitatively by a combination of ¹³C and ¹H n.m.r. The unit structure of petroleum ether insoluble fractions in the lignite consists of one to three aromatic rings with straight-chain alkyl groups, some of which are about 25–30 carbon atoms long.     

褐煤干燥技术发展及应用现状

论述了国内外褐煤干燥提质技术的发展现状。针对传统热力干燥在褐煤电厂应用中存在的高能耗、高投资和低安全性等问题,开展了褐煤过热蒸汽干燥机理的试验研究和中试试验。结果表明：过热蒸汽的干燥效果优于常规热空气;中试试验系统能稳定、连续地对褐煤进行干燥,且干燥产品符合褐煤干燥实际工业应用的要求。最后提出了过热蒸汽预干燥低质煤提质洁净煤技术（SCU技术）,对其在节能、安全等方面的技术先进性作了具体的对比分析,结果表明：SCU技术节能节水、安全性高,符合中国可持续发展战略和节能减排的要求。     

Recovery,fractionation and study of oils from a lignite

Oils from a lignite (Teruel, Spain) were studied. They were obtained by catalytic depolymerization, by reacting an aromatic substrate (tetralin), Lewis acid catalyst (BF₃) and the lignite (oil A) or asphaltenes (oil B) at atmospheric pressure and temperatures <220 °C. The A and B oils were fractionated on an alumina-silica gel dual column into their saturated, mono- and diaromatic, polyaromatic and polar components by elution with hexane, hexane-benzene, benzene and methanol-diethyl ether-benzene respectively. The elemental analysis, average molecular weight, i.r. and ¹H n.m.r. spectroscopy and aromaticity data of these subfractions were studied.     

成型热解对褐煤成浆性的影响

为提高褐煤水煤浆的成浆性,以新疆褐煤、半焦及型煤半焦为原料,对其成浆性进行对比分析。结果表明:粗细煤粉质量比6∶4,最佳添加剂用量1.2%时,型煤半焦制备的水煤浆成浆性最好,最大成浆浓度为60.1%,表观黏度为1153 mPa·s。在级配、添加剂用量相同的条件下,褐煤和半焦的最大成浆浓度分别为48.7%和56.8%。煤样工业分析和表面结构研究表明随着提质改性程度的增加,新疆褐煤、半焦及型煤半焦的水分和挥发分依次降低,固定碳升高,孔半径减小,比表面积增大,孔容积变化不明显。说明褐煤经热压提质改性后,煤化度升高,结构渐趋紧密,孔隙率降低,有利于提高褐煤成浆性。     

Low-temperature pyrolysis of Texas lignite,basic extracts and some related model compounds

Low-temperature (400 °C) pyrolysis of Texas lignite produced volatile products typical of coal tars, with tar evolution beginning at about 300 °C. n-Alkanes up to about C₃₀ were observed among the products and these were accompanied by smaller but significant amounts of 1 -alkenes. Similar pyrolyses were performed on pyridine extracts and sodium hydroxide extracts of lignite. The alkanes and alkenes were seen among the pyrolysis products from the pyridine extracts and from the residual lignite from both types of extractions, but they were not seen among the pyrolysis products from the sodium hydroxide extracts. Pyrolyses of some model compounds suggested that dealkylation of alkyl-substituted arenes can be significant at 400 °C and can account for the production of the alkanes and alkenes from the lignite.     

褐煤及其热解产品利用现状

为了提高褐煤利用率,介绍了国内褐煤资源的储量形态、分布。分析了目前褐煤的利用途径,包括共伴生资源的利用、直接燃烧、干燥脱水与成型、气化、液化、制水煤浆与热解。并进一步分析了褐煤热解气、液、固产品的利用方向。提出了褐煤半焦利用的新方法,即利用半焦干法气化,或将半焦和热解废水等制成水煤浆,通过湿法气化制得合成气,再通过甲烷化催化剂将合成气制成甲烷,或将合成气通过费托合成制成汽油柴油。     

Coliquefaction studies of waste polymers and lignite influenced by acidic and oil‐soluble catalysts

A detailed study of postconsumer polymer coliquefaction with lignite influenced by two acidic and two oil‐soluble catalyst precursors is presented in this article. The conversion of reacting solids into gaseous and liquid products was determined in four initial series of coprocessing experiments performed with and without catalysts on a suite of four heavy organic solvents. Based on the results obtained, two newer series of experiments were also designed and carried out, aimed at the optimization of this complex transformation using this time lignite oxidatively pretreated. It was found that the mentioned hydroconversion is a promising way of hydrocarbon synthesis and that oxidatively pretreated lignite proved superior to the raw material. It was also found that the oil‐soluble catalysts employed indicated a particularly noticeable activity increase, influencing, thus, the efficacy of the conversions achieved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1323–1330, 2000     

逐级化学提取(SCEE)技术及其在煤微量元素赋存状态研究中的应用

概述了逐级化学提取(SCEE)技术的分析方法,介绍了SCEE技术的发展历程和其中典型的Tessier、BCR权威分析方法,综述了近一段时间国内外SCEE技术在煤微量元素赋存状态研究方面的应用状况,并就该技术在赋存状态研究方面仍存在的问题进行了两方面探讨:(1)煤中不同赋存状态元素在逐级化学提取中的归属问题;(2)逐级化学提取法分析元素形态存在的问题。     

Trace element geochemistry of the Obed Mountain deposit coals, Alberta, Canada

This study reports on the elemental concentrations and vertical variation of coal seams from the Obed Mountain deposit, Alberta Foothills, Canada. Results from two sections of Seam 1 show that the major elements (i.e. Al, Fe, Mg, K, Na, Ti, and Si) have high concentrations in intervals having high ash content, with the only exception of Ca. Similarities are apparent, in both sections, in the vertical variations of Th, U, Se, and Zn; Rb, Cs, and K; Sb, Mo, and W; Mn and Sr; and Ba, Cr, Co, Hf, and Sc. These similarities are also evident among the REEs, notably between Ce and La; also between Dy, Eu, and Sm. Most elements, with the exception of Ba and Sr are slightly more concentrated in Section 2 of Seam 1, located approximately 1.5Fig. km away from Section 1. Compared to Seam 1, Seam 2 has lower mean concentrations of elements. Boron in the coal ranges from 27 to 100 ppmw, though most values are less than 50 ppmw. Boron concentrations suggest a freshwater depositional environment. The element is depleted in the sedimentary partings (12–29 ppmw only) and is enriched in the coal interval near the roof and immediately beneath the partings. This enrichment shows possible downward mobilization of boron. Vertical variations of elements are helpful in delineating the boundaries between coal and sedimentary partings in the succession. The Obed Mountain coals are “clean” by world standards and their elemental concentrations are comparable with those in coals of a lower rank from the same coal formation used for power generation in Alberta. All sedimentary partings have low concentrations of Ba, Hf, Sc, Sr, Ta, Th, U, and REEs; this, along with the absence of an Eu negative anomaly suggests a non-volcanic origin for the partings.     

Certification of the contents of some trace elements in a coal

The preparation of a coal reference material to be used in trace element analysis is described, as well as the tests to ascertain the homogeneity and stability of the material. Several analytical methods were applied by several laboratories to certify the contents of As, Cd, Cr, Co, F, Mn, Hg, Ni, Pb and Zn. The procedure followed for certification is explained.     

褐煤提质系统若干问题的探讨与分析

分析了"褐煤固体热载体快速热解技术"工业化工艺系统存在的煤气净化、焦油分离、含酚废水的处理及提质产品难以储存等问题,并提出了改进工艺流程、制含酚水煤浆、制提质煤型煤等相应的解决方案。